This invention concerns the dimension control of the rolling material of a continuous rolling machine having a hole roll, for example, a bar steel mill or a wire mill.
An example of the structure of a continuous rolling machine of this type is shown in FIG. 1.
FIG. 1 shows a continuous rolling machine comprising i mill stands, wherein are illustrated a #1 mill stand 1, a #2 mill stand 2, an #i-1 mill stand 3, an #i mill stand 4, and a rolling material 5.
FIG. 1 illustrates a so-called VH type rolling machine, wherein horizontal mill stands (odd numbered stands in FIG. 1) and vertical mill stands (even numbered stands in FIG. 1) are alternately arranged.
For instance, the #i-1 mill stand 3 is a vertical mill performing rolling in the X direction wherein bi-1 represents the laterial dimension and hi-1 represents the vertical dimension at the exit of the #i-1 mill stand 3. On the other hand, the #i mill stand 4 is a horizontal mill performing rolling in the Y direction, wherein bi represents the lateral dimension and hi represents the vertical dimension at the exit of the #i mill stand 4.
Conventional continuous rolling machines such as bar steel and wire mills employ a non-tension control method (AMTC) for reducing the tension between the mill stands to zero. However, a dynamic control method has not yet been used for the following reasons.
(1) there have been no severe requirements on the dimension of the products, and PA1 (2) mill elongation due to a change in the load during rolling is small (which makes the dimensional accuracy of the products better, since the effect of transferring the change at the inlet to the exit is decreased).
Accordingly, no particular control has been exercised in the conventional control system over the change in dimensions relative to changes in the temperature of the rolling material or the like, worsening the dimensional accuracy.